482 C. H. HITCHCOCK GEOLOGY OF DIAMOND HEAD, OAHU 



largely composed of the same material. It was stated above that over 

 500 feet of limestone underlies the south end of Diamond head, and only 

 30 feet in the well at the Queens hospital adjacent to Punchbowl. As 

 the volcanic ejection brought up the underlying rock, Diamond head 

 should show very much more of it than Punchbowl. It is also on the 

 seashore adjacent to the reef from which come quantities of eolian cal- 

 careous sand. Punchbowl is half a mile distant from the seashore, and 

 therefore would not be expected to be supplied so abundantly with blown 

 sand. 



An examination on the inwardly dipping layers near the highest point 

 of Diamond head reveals a very liberal supply of limestone. It was here 

 that I found coral and shells in 1883. The photograph in plate 61, 

 figure 1, shows the abundant supply in the layers of tuff in the fore- 

 ground on the right-hand side. The standpoint is quite near the sum- 

 mit, and the view was taken to show the rim of the cone, the interior, 

 and the black promontory of Kupikipikio in the distance. 



In this connection it is proper to advert to the abundance of limestone 

 in the inside of the crater at Salt lake. Not merely are the fragments 

 abundant, but the original reef itself must be present.* The western 

 Koko head is equally prolific with limestone blocks, though from a hasty 

 examination I am not prepared to say that the original ledge can be de- 

 tected. The limestone has not been seen in the lowest part of the inside 

 of Diamond head, but there is a pond there entirely dry except after 

 heavy rains. This is shown in plate 60, figure 2, and plate 61, figure 1, 

 shows the character of the erosion on the west side of the Head. 



The Talus-breccia Deposit with Land Shells 



At the southern base of Diamond head, at a quarry not far from the 

 terminus of the electric road (1905), is an extensive excavation in a 

 talus-breccia of tuff with a calcareous cement. This carries shells of 

 Lepachtinia, Helicona, Pitys, Succinea, Pupa, and Helix lamblata, as 

 heretofore reported. A similar deposit may be found skirting the base 

 of the cone, probably on every side as well as in the inside, but it is seen 

 to the best advantage where the new road has cut into it between the 

 quarry and the lighthouse. Near the lighthouse the specimens of shells 

 are particularly abundant because of the greater magnitude of the ex- 

 cavations. To the list given above may be added Amastra and Endo- 

 donta, and Professor G. H. Perkins found in addition, lower down the 

 cliff, the remains of Crustacea. Mr C. Montague Cooke, of the Bishop 

 Museum, has discovered additional localities of these shells upon Eocky 



* Geology of Oahu, p. 38. 



